Fuel control means



May 14, 1946. D. s. HERSEY- FUEL CONTROL MEANS Filed Dec. 14, 1940 1 m I m INVENTORY Donald S. Her.s 9 JW 4. M

ATTORNEY.

Patented May 1 4, 1946 I FUEL CONTROL MEANS Donald S. Hersey, West Hartford, Conn., assignor .to United Aircraft Corporation, East Hartford,

Conn., a corporation of Delaware Application December 14, 1940, Serial No. 370,160

21 Claims. (Cl. 123 -140) This invention relates to improvements in means for supplying a regulated quantity of fuel to an engine,such as an internal combustion engine, and hasfor an object the provision of a simplified, light weight mechanism for accurately metering the engine fuel to maintain the desired fuel-air ratio for the engine intake under various engine operating conditions.

A further object resides in the provision of means effective to accurately and continuously detect the density of the engine intake air and to meter the engine fuel supply in accordance. with the product of the density and volumetric rate of flow of the intake air.

Other objects and advantages will be more particularly-pointed out hereinafter or will become apparent as the description proceeds.

' Inthe accompanying drawing, in which'like reference numerals are used to designate similar parts throughout, there isillustrated a suitable mechanical embodiment for the purpose of disclosing the invention. The drawing, however, is for the purpose of illustration only and is not pneumatic motor device, generally indicated at 84. The device 34 comprises a generally cylindrical casing 88 divided into two substantially to be taken as limiting or restricting the invention as it will be apparent to those skilled in the art that various changes in the illustrated arrangement may be resorted to without in any way exceeding the scope of the In the drawing,

Fig. 1 is a diagrammatic illustration of invention.

engine fuel control apparatus constructed accates an internal combustion engine which may be a radial air-cooled type of engine, such as is conventionally employed for the propulsion of aircraft, although the invention is in no way .limited to any particular type of internal combustion engine. Such an engine may have a crankcase portion, as indicated at it, upon which are mounted a number of cylinders, one of which is indicated at l4, and may have a supercharger section I8 having an air intakeduct l8 leading to an impeller 28 which discharges into a diffuser section 22 connected with the various cylinders by suitable means, such as the individual intake pip one of which is indicated at 24. Fuel may be supplied to the engine through an injection nozzle 28 which distributes the fuel into the intake airstream entering the impeller 28 so that the fuel is thoroughly mixed with the intake air as the air and fuel pass through the impeller and the difluser 22.

The intake air may be constantly sampled and equal chambers by a flexible transverse partition 38. The conduit 82 is connected with the cham-' her, as indicated at 48, at one side 'of the diaphragm 38 while the conduit 88 is connected with the chamber, as indicated at 42, at the opposite sideof the diaphragm. A. red 44 is operatively connected with the diaphragm 38 and is connected to the casing 38 by suitable flexible seals,.

as indicated at 48 and 48, in such a manner that a pressure diiferential between the chambers 48- and 42 acting upon the diaphragm 38 will move rounding the casing will not affect the force exerted by the diaphragm 88 because of the balancing effect of the substantially equal areas of the flexible seal members 48 and 48. v l One end of the rod 44 is connected to a control ring 48 of a variable displacement fluid pump, generally indicated at 88, and the other end passes through a compression spring 8| which presses against the diaphragm 88 and casing 84 plurality of radially disposed vanes 58 which rotate in the member 48 and pump fluid, such as fuel, from the pump intake 82 to the pump outlet 54 whenever the member 48 is positioned eccen- 5 trically with respect to the rotor 58. As the rod member 44 moves to change the eccentricity of the member. 48 relative to the rotor 58 the pump displacement for each revolution will be varied from substantially zero when the two members are'exac y concentric to the-maximum displacement when the member 48 reaches its position of maximum eccentricity with respect to the member".

As the pump is driven by the engine at some constant ratio to engine speed, the output of the pump would normally vary in directproportion to the speed of the engine for any flxed position of member 48, and the fuel supply to the engine would then be a direct function of its density continuously detected by a density de-. engine speed. The control unit 28 modifies the displacement of the pump 50 in accordance with variations in density of the engine intake air so that the output of the pump becomes a function of the product of engine speed and intake air density to maintain the engine fuel supply at a substantially constant proportion to the engine air supply as will be explained in greater detail hereinafter. e

The characteristics of unit 28 may be modified so that the output of the fuel pump becomes a function of the product of the engine speed and the charge density and the volumetric efficiency of the engine.

With this arrangement, if the engine speed is unchanged during a change in density, as by changing the altitude of the airplane or by throttling at. the intake air entrance, the fuel supply will be changed, and, in the event the density of the intake air decreases under these conditions, the fuel supply will be accordingly diminished while, if the density of the intake air is increased, as by opening the throttle 60, while maintaining the engine speed constant, as by means of a controllable-pitch propeller, the fuel supply will be increased to meet this increased engine power condition The density detecting device generally indicated at 28 may be a device such as is particularly illustrated and' described in my co-pending suitable means, such as the flexible drive 64, One

side of this pump is connected with the air intake duct [8 through a suitable branch conduit 68 and the other side is connected with the interior of a chamber 68 which is connected with an adjoining chamber l through a fixed orifice 12 provided in a transverse partition 14 separating the two chambers. the engine intake system between the throttle 60 and the engine cylinders so that density variations in the air supplied to the cylinders occasioned by operation of the throttle will be imposed on the fuel regulating device and the chamber 78 is connected with the air intake duct l8 through a branch channel I6 spaced from the channel 86. The effective area of the orifice I2 is controlled by a movable plug I8 which is urged towards orifice closing position by means of a coiled compression spring 88 and is moved to orifice opening position by centrifugal force exerted on flyballs 82 driven from the pump shaft 84 through a suitable gear train, generally indicated at 88. The plug shaft 88 may extend beyond the orifice and into a guide 98 provided with a stop 92 to prevent the plug from entirely closing the orifice at any time. With this arrangement the pressure differential between the chambers 88 and ID will be proportional to the density of the air flowing through the air intake duct l8 since the pressure head necessary to force a constant volume of air through a constant orifice variesas the air .density and this relation is maintained in the present apparatus by varying the orifice directly as the air volume varies with variations in the speed of the. constant displacement pump. This pressure differential will be transmitted through the conduits 30 and 32 to the fluid motor 34 to adjust the displacement of the pump 50 in accordance with variations in t density of the engine intake air. Suitable The conduit 66 is connected to means may be provided, if desired, to richen the mixture at high engine power rates with accompanying high speed to protec't'the engine, and to meter automatically the fuel for engine idling operation. This 'may be conveniently accomplished by giving the movable plug 18 a contour such that the area of the opening between the side of this plug and the edge of the orifice I2 will be varied in a predetermined manner with variations in the engine speed.

' The contour of the plug 18 may also be designed to compensate for changes in the volumetric efficiency of the engine with changes in engine'speed so that, if the volumetric efficiency decreases above a particular speed, the contour of the plug will proportionately modify the rate of change of the opening between the plug and the orifice 12 as the engine speed increases above the particular rate. The device might also be compensated for variations in the volumetric efliciency of the engine in other ways such as by selecting a suitable variable rate spring of proper characteristics for the spring 80, or by providing an additional orifice through the partition 14, a plug for varying the area of the additional orifice and an engine speed responsive governor for controlling the plug.

A manual mixture control may be incorporated by providing a connecting channel 94 between the channels 38 and 32 and intercepting this connecting channel with a manually controllable the capacity of the fuel pump.

The air may flow through the device 28 in either direction but, for certain installations, it has been found desirable to have the blower 62 draw the air through the chambers 10 and B8 rather than force it through. The air from the duct l8 would then flow through the channel 16 to the chamber 70, through the orifice 12 to the chamber 68, then through the blower 62 and back to the duct through the channel 66. Under these conditions, if the engine were rapidly accelerated there would be a sudden increase in the pressure above the diaphragm 38 which might result in an over rich mixture being temporarily supplied to the engine. This condition can be controlled by providing in the line 32 a restriction, as indicated at 98, properly dimensioned to retard the transmission of the pressure rise in the chamber 10 to the upper side of the diaphragm 38. This provides a means of controlling the fuel charge during acceleration of the engine.

If desired, a pressure type gauge 10 may be connected between the lines 38 and 32 to indicate the pressure head across the orifice 12. If the orifice varying plug then varies the orifice I .luch

a manner that the pressure head across the orifice is proportional to the product of intake air density and volumetric efiiciency of the engine, the gauge dial can be calibrated to read in units of indicated mean effective pressure which is senting engine speed, will indicate the rate of fuel fiow to the engine.

While a suitable mechanical embodiment has been illustrated in the accompanying drawing and hereinabove described for the purpose of disclosing theinvention, it is to be understood that the invention is not limited to the particular arrangement so illustrated and described but that such changes in the size, shape and arrangements of the various parts may be resorted to as come within the scope'of the subjoined claims.

Reference is made to my copending application Serial No. 311,153 (filed December 2'], 1939), which shows and claims subject matter shown and not claimed in this application.

Having now described the invention so that others skilled in the art may clearly understand the same, what it is desired to secure by Letters Patent is as follows:

1. Means for supplying fuelto an engine, having an air intake duct, in a predetermined proportion to the weight of air flowing through said duct per'unit of time comprising, a fluid pump having a definite volumetric capacity for each operating speed, a fluid conduit connected with said pump and said air intake duct, an orifice in said conduit for establishing a pressure differen tlal proportional to the fluid density, means for varying the area of said orifice in accordance variations in pump speed in the operative of the device, an engine driven controllable displacement fuel supply pump, and a fluid pressure responsive devicev actuated by said pressure dif-,

with the speed of said pump to render said presvtioning the amount of fuel supplied to said engine to the weight of engine intake air flowing through said intake duct per unit of time comprising, an engine driven .fiuid pump having a definite volumetric capacity for each operating speed connected at both sides to said intake duct,

-a restriction in the connection at one side of said pump, speed responsive means for varying the free area through said restriction in accordance with variations in the speed of said pump to ply pump in accordance with variations in the a density of the engine intake air.

3. The arrangement as set forth in claim 2 in which the engine is provided with a throttle and one or more cylinders and one side of said fluid pump is connected to the engine air induction ferential and operatively connected with said fuel supply pump to vary the displacement of said fuel supply pump in accordance with variations in said pressure differential. v

5. In combination, a fluid conduit, a fluid pump in said conduit having a definite volumetric capacity for each operating speed, a variable area orifice in said conduit, means for driving said pump, means for varying the area of said orifice in accordance with the speed of said pump, and a device connected with the spaces at opposite sides of said variable area orifice operated by the pressure difference across said orifice comprising, a controllable displacement pump and a fluid pressure responsive device for varying the capacity of said pump in accordance with variations in 'said pressure difference.

6. Thearrangement as set forth in c1aim 2j including a manually controllable air bleed be-' tween the opposite sides or said fluid pressure actuated device to provide a manual mixture control for said fuel supply system.

7. The arrangement as set forth in claim 4 in which said movable means for varying the area of said orifice is provided with a curved orifice varying portion for varying said orifice area at a rate proportional to variations in the volumetric efficiency of said engine in addition to variations roportional to changes in pump speed.

I 8. The arrangement as set forth in claim 4 including a specially shaped portion on said means for varying said orifice area at a predetermined rate in addition to variations proportional to changes in pump-speed to vary the fuel-air ratio of the mixture supplied to the engine at at least one end of the quatitatlve range of fuel upp y-- 9. The. arrangement asset forth in claim 4 including means for varying the area of said orifice operative to vary said orifice area in proportion to variations in thevolumetric efficiency of said engine over the engine speedrange and in accordance with a predetermined fuel to air ratio at different points in the quantitative fuel supply range in addition to said variation proportional to changes in engine speed.

'10. In combination with an engine having an air intake duct, and a power regulating throttle, means for continuously sampling the air in said air intake duct between said engine and said throttle during engine operation and providing a pressure head proportional to the product of the density of said air and the volumetric emciency of said engine. and pressure responsive indicating of predetermined maximum area in the connection between one side. of said pump and said air induction system, movable means for varying the 70 area of said orifice, means responsive to pump speed for controlling the movements of said movable means to maintain a pressure differential across said orifice proportional to the density of the air flowing therethrough regardless of 7 I 12. In combination with an engine having a means actuated by said pressure head and callbrated to continuously disclose the indicated' mean effective pressure of the gas in the cylinders of said engine during engine operation.

11. In combination with an engine having a restricted passage through which intake air is forced, means for maintaining the flow rate' through the, restricted passage so that the pressure differential across the restriction varies in accordance with changes in intake air density, means for injecting fuel into said intake air, means for measuring the quantity of fuel in- Jected, and means actuated by said pressure differential for adjusting said measuring means to maintain the correct proportion of fuel to air for diflerent intake air densities.

restricted passage through which intake air is forced, means for maintaining the flow rate through the, restricted passage such that the pressure differential across the restriction varies in accordance with changes in intake air density, an engine driven variable volume pump for injecting fuel into said intake air, and a device .actuated by said pressure differential across said jecting fuel into said intake air, means for measuring the quantity of fuel injected, and means actuated by said pressure differential for adjusts ing said measuring means to'maintain the correct proportion of fuel to air for different intake air densities and for changes in engine volumetric eificiency.

14. In combination with an engine having a restricted passage through which intake air is forced, means responsive to changes in engine speed for varying the free area of said restricted passage, said means constructed and arranged so that the pressure differential across the restriction varies in accordance with intake airvdensity and a speed induced engine variable, such as v01- umetric efficiency, means for injecting fuel into said intake air, means for measuring the quantity of fuel injected, and means actuated by said pressure differential for adjusting said measuring means to maintain the correct proportion of fuel to air for different intake air densities, and different engine speeds.

15. Charge forming apparatus for an internal combustion engine having an air intake system and a variable capacity fuel supply means having a driving connection with said engine comprising, engine driven means for continuously forcing a sample of intake air through a restricted orifice, speed responsive means for varying the restriction of said orifice in accordance with variations in engine speed, and means actuated by the pressure drop across said orifice to regulate the output capacity of said fuel supply means in accordance with variations in said pressure drop.

16. Charge forming apparatus for an internal combustion engine having an air intake system and an engine driven fuel supply means the output capacity per operating cycle of which is adjustable, a pneumatic shunt circuit having a restriction therein connected at both sides to said air intake system, an engine driven pump hav ing a constant volumetric capacity for each operating cycle interposed in said circuit for continuously forcing a measured quantity of intake air therethrough, speed responsive means for varying the magnitude of said restriction in direct proportion to variations in engine speed, and a pneumatic device connected with said shunt circuit and with said fuel supply means and actuated by variations in the pressure drop across said restriction to vary the output capacity of said fuel supply means in direct proportion to variations in said pressure drop.

17. Charge forming apparatus for an internal combustion engine having an air intake system and a fuel supply means comprising, an intake air sampling device including a casing comprising two chambers connected independently with said air intake system and separated by a transverse partitionhaving an air flow orifice therethrough, a positive displacement engine driven pump interposed in the connection between one of said chambers and said air intake system to maintain a circulation of engine intake air through said chambers and said orifice, means for compensating said-air sampling device for variations in engine speed, and a pneumatic device connected with said chambers and with said fuel supply means and actuated by changes in the pressure differential between said chambers to vary the output capacity of said fuel supply means in accordance with variations in the pressure differential across said orifice.

18. In combination with an engine having a restricted passage through which intake air is pressure differential and operatively connected with said measuring means for adjusting said .measuring means in accordance with variations in said pressure differential, and means for providing a time lag in the application to said fluid pressure responsive device of sudden changes in the pressure differential across said restriction.

19. Fuel control means for an internal combustion engine comprising, a variable capacity fuel supply device, means for determining variations in the product of the engine intake air density and the volumetric efficiency of the engine, and means responsive to the operation of said determining means for varying the capacity of said fuel supply device in proportion to said variations.

20. Fuel supply means for an internal combustion engine comprising, a variable capacity fuel supply device the capacity of which tends to vary directly with variations in engine speed, means for continuously evaluating the product of engine intake air'density and the volumetric efficiency of said engine, and means responsive to the operation of said evaluating means for proportioning the capacity of said fuel supply device to said product.

21. In an engine charge forming apparatus, an engine driven adjustable displacement fuel pump, an air sampling device for continuously passing a sample of engine intake air through a restriction and having meansv operative to maintain a predetermined ratio between the volumetric flow rate of the sample air and the size of the restriction to provide across said restriction a pressure head proportional to the density of said intake air, means actuated by said pressure head and operatively connected with said fuel pump for varying the quantity of fuel delivered per cycle by said pump in accordance with variations in f intake air density to maintain a substantially constant proportion between the weight of intake air and the weight of fuel delivered to said engine in the same interval, and manually operated means for varying said pressure head.

DONALD S. HERSEY. 

